[dm-devel] dm-statistics: report precise timestamps and histogram

[Mikulas Patocka]

On Wed, 19 Aug 2015, Bryn M. Reeves wrote:

> On Wed, Aug 19, 2015 at 06:53:41AM -0400, Mikulas Patocka wrote:
> > On Tue, 18 Aug 2015, Mike Snitzer wrote:
> > > On Tue, Aug 18 2015 at  4:26pm -0400,
> > > Mikulas Patocka <mpatocka at redhat.com> wrote:
> > > > Mike, please submit this patch to the upstream kernel before 4.2 is 
> > > > released, so that the all the kernels that support the options 
> > > > "precise_timestamps" and "histogram" also report these values back.
> > > 
> > > Userspace will have to check the DM ioctl version to know if DM provides
> > > these extra keywords.
> > > 
> > > Mike
> > 
> > But if you don't send it, userspace will forever have to deal with kernels 
> > that don't report this feature back.
> 
> We'd either end up saying some kernels can't support it when they can, or
> have to carry some additional userspace clutter forever to provide a 
> workaround.
> 
> Regards,
> Bryn.

I think you don't need to provide a workaround for kernels that don't 
report it. The workaround would be needed just for 4.2.0 (Mike said he 
will backport the fix to 4.2.1), there is no need to bloat userspace with 
that.

Mikulas